restless · Jul 26, 2023

Hi
Alt was boiling the battery, so disconned it... Ooops... and volts shot up beyond meter scale, blew every light and god knows what else.
Limped the rest of the 700miles off battery from the caravan on jumps thru window and fly wires to run solenoid and similar to starter.
No glow plugs or run..
fuse 3 (sat 1)-run pops immediately
Fuse 18 (elec mirrors) as above
Fuse 17 gloplugs ok.

Apparently there is a relay that has burnt out, a specialist told me if I change that I can go back to starting off the key. Stupid perhaps, but mirrors are good as I drive on both sides of the road (UK/eu/when drunk) often hauling big things, so a very useful mod con.
Alarm has been disabled via a plug in delete programmer, though it is utterly bypassed now anyway.
Looked at schematics, but all the options and poor. Cross referencing of relays/options etc etc just made me wanna puke (on a phone)

So, now 900 miles from home, hope someone can point me in the right direction to hone in on a ruined run critical relay, I dont really want to open every damn one up and inspect!

Fuel guage doesn't go below half any more either, needs keeping an eye on!
Temp guage and Speedo, alt light and oil still good, happy days.

Thanks for reading

sierrafery · Jul 27, 2023

Hi... read your own post and think a bit after you sober up then try to explain again with some sense what's your problem

mystery · Jul 27, 2023

Are you referring to the starter relay or the anti-theft relay

marjon · Jul 27, 2023

Disconnecting the battery when the alternator is broke is never a good idea.

Although some say its a way to test stuff :vb-groan2:

J

Stanleysteamer · Jul 27, 2023

marjon said:
Disconnecting the battery when the alternator is broke is never a good idea.

Although some say its a way to test stuff

J

As in "test to destruction".

PopPops · Jul 27, 2023

marjon said:
Disconnecting the battery when the alternator is broke is never a good idea.

Although some say its a way to test stuff

J

Or at any time the engine is running!

Stanleysteamer · Jul 27, 2023

Generally if an alternator is "boiling the battery" it is because the diode pack is fubar, has the OP even tested the alternator with the engine running to see if it is giving 14 v roughly?
If not, an alternator repair would seem to be the first route to go down before fretting about anything else.

discool · Jul 27, 2023

Stanleysteamer said:
Generally if an alternator is "boiling the battery" it is because the diode pack is fubar, has the OP even tested the alternator with the engine running to see if it is giving 14 v roughly?
If not, an alternator repair would seem to be the first route to go down before fretting about anything else.

Nothing to do with a diode pack, but it will be the regulator thats faulty, if the battery is overcharged when using an alternator to charge.

discool · Jul 27, 2023

mystery said:
Are you referring to the starter relay or the anti-theft relay

Don't hold your breath in finding an anti-theft relay… there isn’t one.

restless · Jul 27, 2023

Thanks to those who actually came forth with something useful.

To others who really didn't get the initial situation, well done for pointing out the obvious. Those that seem to like to pick on mistakes made in a stressful situation, well, sit back in your smug armchair and pontificate.

Sorry, guess I'm used to civility in forums.
I do a lot with old mercedes (om617 /602) and am held in very high regard, primarily by providing accurate and polite guidance on everything from tuning to upgrades. Silly me, guess that etiquette would have been strong in a similar group.

Alternator has been replaced.
Yeah, not such a grand idea unplugging while running, but without a battery and on a time scale....so glad some people are just so amazing that they just know exactly what to do perfectly all the time. Perhaps at the price of a sense of humour.

To clarify:
I would simply like to start my engine on the key.
I was told by a french landy pro that there is a burnt out relay as part of the immobiliser that is probably locking out IP and starter sol. (It is after all what it does...)

I was hoping somebody may have knowledge as to where to find it.
I have barely any tools and am 900miles from home.

It starts and runs, and stops, I would like to remove the emergency wires running from engine bay through the window.
I could easily wire in a start button (if I were at home), just thought it would be easier/better to change a wrecked relay.

discool · Jul 27, 2023

Relay is in drivers footwell, yellow colour if original, and in the centre of three on the bottom row, unplug if it looks or smells iffy or test it with a multimeter all standard stuff, maybe quicker to just replace.

A temporary fix just for cranking, install a wire from battery pos via a push switch to the relay coil or direct to the starter solenoid, that will also be an overlay if you have ‘spider’ immobiliser fitted and has inhibited that function.

A temp solution should last till u return.

Shippers · Jul 27, 2023

discool said:
Ok post #3 shows the location of a starter relay, unplug if it looks or smells iffy or test it with a multimeter all standard stuff, maybe quicker to just replace.

A temporary fix just for cranking, install a wire from battery pos via a push switch to the relay coil or direct to the starter solenoid, that will also be an overlay if you have ‘spider’ immobiliser fitted and has inhibited that function.

A temp solution should last till u return.

Exactly what I did to my van except for coil as it's diesel you dont even need a switch just a wire from starter and one for battery pos and ehmm (hot wire it) touch them together and crank...

Stanleysteamer · Jul 28, 2023

discool said:
Nothing to do with a diode pack, but it will be the regulator thats faulty, if the battery is overcharged when using an alternator to charge.

I thought the diode pack WAS the regulator, I must be missing technical terms as usual!
Anyway, I meant the gubbins in one end of the alternator that regulates how much power/voltage/current/ whatever is chucked out and into the system which also incidentally charges the battery.

Don't know if a motor vehicle regulator uses a Zenner diode but if it does then I might just be right.

[Solved] What type of diode can be used as a voltage regulator?

CONCEPT: Zener diode: It is a highly doped p - n junction which is not damaged by high reverse current. It can operate continuously, without being damaged i

testbook.com

Stanleysteamer · Jul 28, 2023

discool said:
Nothing to do with a diode pack, but it will be the regulator thats faulty, if the battery is overcharged when using an alternator to charge.

Which apparently could even be part of the eCU.
Who'd a thort it.

https://www.my-cardictionary.com/electrics/alternator-regulator.html

Stanleysteamer · Jul 28, 2023

Hey @restless, we are trying to help you and if you read enough on the forum you'll know that when it comes to electricals there is no one really to touch @sierrafery it is just that he can get a bit short with people.
Do feel for you being 900 miles from home and stuck.
Sincerely hope you get it sorted!!

PopPops · Jul 28, 2023

Stanleysteamer said:
Hey @restless, we are trying to help you and if you read enough on the forum you'll know that when it comes to electricals there is no one really to touch @sierrafery it is just that he can get a bit short with people.
Do feel for you being 900 miles from home and stuck.
Sincerely hope you get it sorted!!

+1^^

The amount of time @sierrafery spends helping people is amazing, as is his knowledge.

Stanleysteamer · Jul 28, 2023

restless said:
Thanks to those who actually came forth with something useful.

To others who really didn't get the initial situation, well done for pointing out the obvious. Those that seem to like to pick on mistakes made in a stressful situation, well, sit back in your smug armchair and pontificate.

Sorry, guess I'm used to civility in forums.
I do a lot with old mercedes (om617 /602) and am held in very high regard, primarily by providing accurate and polite guidance on everything from tuning to upgrades. Silly me, guess that etiquette would have been strong in a similar group.

Alternator has been replaced.
Yeah, not such a grand idea unplugging while running, but without a battery and on a time scale....so glad some people are just so amazing that they just know exactly what to do perfectly all the time. Perhaps at the price of a sense of humour.

To clarify:
I would simply like to start my engine on the key.
I was told by a french landy pro that there is a burnt out relay as part of the immobiliser that is probably locking out IP and starter sol. (It is after all what it does...)

I was hoping somebody may have knowledge as to where to find it.
I have barely any tools and am 900miles from home.

It starts and runs, and stops, I would like to remove the emergency wires running from engine bay through the window.
I could easily wire in a start button (if I were at home), just thought it would be easier/better to change a wrecked relay.

It might have been handy if you had said in your first post that you had replaced the alternator and that charging and battery boiling was no longer an issue. It did seem to be the big issue. Or one of them.

I thort, as others did, that hot wiring the starter was so obvious and simple it wouldn't have presented you with a problem.

Shippers · Jul 28, 2023

Stanleysteamer said:
thort, as others did, that hot wiring the starter was so obvious and simple it wouldn't have presented you with a problem.

obviously it wasnt obviously simple...but it is to some of us had to do it to van recently when it wouldnt crank...but thats another story which took a week to sort...

restless · Jul 29, 2023

Hi
Thanks guys, much appreciated.
All the hotwire stuff is holding out fine. I'm no stranger to vehicle electrics, however the disco has an overwhelming quantity of cleverness.
Would like to pinpoint any currently burnt items and repair or take ooc, mainly as I would rather not have something that may become intermittent.
Will go see if I can find that relay

Stanleysteamer · Jul 29, 2023

Shippers said:
obviously it wasnt obviously simple...but it is to some of us had to do it to van recently when it wouldnt crank...but thats another story which took a week to sort...

I can remember a neighbour doing it to our Morris 1000 Traveller back when I was nipper in about 1963. Real "hot wiring" not jump starting.
For some reason we had the key to open the rear door but not the front one. My dad had gone to work with it. So I scrambled over the seats and opened up. He "crossed the wires" and we could pull the starter, so mum took us to school.
Of course this refers to ignition not working not the starter.
Starter electrics have a notorious problem when it comes to the contacts and @restless I put up a thread about how to get the wretched beast off and change them. But this is not your problem, probably, yet!

Maybe Mercedes never have electrics problems!!

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